When do the 7 days start?

Hello,
My husband and I will travel to Japan later this year for 9 days. We would like to get the 7 day pass. If we collect on day of arrival, does it "start" from then or from the first time we use it?
Also, as we live in a country with a very poor postal service, can you confirm that we can advance buy and collect on arrival in Japan?
Thanks so much
MCF